Many medical procedures are now available and are being used to remove calculi, stones and the like, which form in body passages, such as kidney stones in kidneys or the ureter, and gallstones in bile ducts. These procedures involve fragmentation or disintegration of the stones, calculi, or other objects by applying energy to them. For instance, kidney stones are typically treated by ultrasonic lithotripsy, electrohydraulic lithotripsy, electro-shock wave lithotripsy (ESWL), laser ablation, laser lithotripsy, and other procedures.
While these procedures are used successfully each year on thousands of patients, some drawbacks remain. For example, when the stones or calculi are fragmented, smaller pieces are formed and must be removed. However, many of these small pieces or fragments may move in undesirable ways because of the retrograde irrigation fluid required for visualization during these procedures. For instance, fragments of a kidney stone may move from the ureter into the kidney or into the calices of the kidney. Many devices are known for anchoring catheters within various body passages or for removing undesirable materials from them. However, these devices generally are not adapted for preventing the migration of fragments from stones, calculi, or other objects within body passages. Such devices are typically not suitable or acceptable for preventing such migration.
It would be useful to have a filter or “catcher” upstream of the stone or calculus, so that after fragmentation, the filter or catcher would capture fragments and prevent them from going upstream or in other undesired directions. For example, ureteral anchors or other catheter anchors, such as a balloon of a Foley catheter could be used to prevent migration, but the balloon is not porous and would not be useful in capturing fragments or calculi after the application or dispersion of energy from an energy source.
A number of devices have been introduced in an attempt to solve this problem. One device is disclosed in WO 98/29043, a ureteral stone occluder having a braided filter. This device has a guide wire and a collapsed mesh or filter at the distal end. The mesh is advanced beyond the stone or calculus and is then expanded before lithotripsy. This device, however, requires sufficient room for the surgeon or technician to advance the filter beyond the occlusion. In another example, U.S. Pat. No. 6,096,053 uses a sheath and a basket, the basket having a number of legs in a generally spiral-shaped net for capturing calculi or stones. However, this device may not be able to move upstream of the device before fragmentation; and the net does not appear to be sufficiently fine for capturing smaller fragments or calculi. U.S. Pat. No. 6,517,550 is directed to a foreign body retrieval device or snare. While this device will likely be able to move upstream of a stone or calculus, it does not appear to be suitable for snaring and capturing small stones or fragments.
What is needed is a device that can overcome the difficulties mentioned above, that is, a device that may be advanced beyond or upstream or downstream of an object or a stone, then expanded or enlarged to effectively block or trap the object or stone. The device will also desirably trap the small particles resulting from lithotripsy or laser operations on the stone or other object. The device will preferably also be easy to collapse and remove from the patient without trauma.